/*
 * Copyright 2004-2011 H2 Group. Multiple-Licensed under the H2 License,
 * Version 1.0, and under the Eclipse Public License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.fulltext;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.DateTools;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.*;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
import org.h2.api.Trigger;
import org.h2.command.Parser;
import org.h2.engine.Session;
import org.h2.expression.ExpressionColumn;
import org.h2.jdbc.JdbcConnection;
import org.h2.tools.SimpleResultSet;
import org.h2.util.New;
import org.h2.util.StatementBuilder;
import org.h2.util.StringUtils;
import org.h2.util.Utils;

import java.io.File;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;

/*## LUCENE2 ##
import org.apache.lucene.index.IndexModifier;
import org.apache.lucene.search.Hits;
//*/
//## LUCENE3 ##
//*/

/**
 * This class implements the full text search based on Apache Lucene.
 * Most methods can be called using SQL statements as well.
 */
@SuppressWarnings("deprecation")
public class FullTextLucene2 extends FullText {

    /**
     * Whether the text content should be stored in the Lucene index.
     */
    protected static final boolean STORE_DOCUMENT_TEXT_IN_INDEX = Utils.getProperty("h2.storeDocumentTextInIndex", false);

    private static final HashMap<String, IndexAccess> INDEX_ACCESS = New.hashMap();
    private static final String TRIGGER_PREFIX = "FTL_";
    private static final String SCHEMA = "FTL";
    private static final String LUCENE_FIELD_DATA = "_DATA";
    private static final String LUCENE_FIELD_QUERY = "_QUERY";
    private static final String LUCENE_FIELD_MODIFIED = "_modified";
    private static final String LUCENE_FIELD_COLUMN_PREFIX = "_";

    /**
     * Initializes full text search functionality for this database. This adds
     * the following Java functions to the database:
     * <ul>
     * <li>FTL_CREATE_INDEX(schemaNameString, tableNameString,
     * columnListString)</li>
     * <li>FTL_SEARCH(queryString, limitInt, offsetInt): result set</li>
     * <li>FTL_REINDEX()</li>
     * <li>FTL_DROP_ALL()</li>
     * </ul>
     * It also adds a schema FTL to the database where bookkeeping information
     * is stored. This function may be called from a Java application, or by
     * using the SQL statements:
     *
     * <pre>
     * CREATE ALIAS IF NOT EXISTS FTL_INIT FOR
     *      &quot;org.h2.fulltext.FullTextLucene2.init&quot;;
     * CALL FTL_INIT();
     * </pre>
     *
     * @param conn the connection
     */
    public static void init(Connection conn) throws SQLException {
        Statement stat = conn.createStatement();
        stat.execute("CREATE SCHEMA IF NOT EXISTS " + SCHEMA);
        stat.execute("CREATE TABLE IF NOT EXISTS " + SCHEMA
                        + ".INDEXES(SCHEMA VARCHAR, TABLE VARCHAR, COLUMNS VARCHAR, PRIMARY KEY(SCHEMA, TABLE))");
        stat.execute("CREATE ALIAS IF NOT EXISTS FTL_CREATE_INDEX FOR \"" + FullTextLucene2.class.getName() + ".createIndex\"");
        stat.execute("CREATE ALIAS IF NOT EXISTS FTL_SEARCH FOR \"" + FullTextLucene2.class.getName() + ".search\"");
        stat.execute("CREATE ALIAS IF NOT EXISTS FTL_SEARCH_DATA FOR \"" + FullTextLucene2.class.getName() + ".searchData\"");
        stat.execute("CREATE ALIAS IF NOT EXISTS FTL_REINDEX FOR \"" + FullTextLucene2.class.getName() + ".reindex\"");
        stat.execute("CREATE ALIAS IF NOT EXISTS FTL_DROP_ALL FOR \"" + FullTextLucene2.class.getName() + ".dropAll\"");
        try {
            getIndexAccess(conn);
        } catch (SQLException e) {
            throw convertException(e);
        }
    }

    public static void deleteRecursive(String fileName) {
        if (new File(fileName).isDirectory()) {
            String[] list = listFiles(fileName);
            if (list != null) {
                for (String l : list) {
                    deleteRecursive(l);
                }
            }
        }

        new File(fileName).delete();
    }

    private static String escapeMetaDataPattern(String pattern) {
        if (pattern == null || pattern.length() == 0) {
            return pattern;
        }
        return StringUtils.replaceAll(pattern, "\\", "\\\\");
    }

    private static String[] listFiles(String path) {
        File f = new File(path);
        try {
            String[] list = f.list();
            if (list == null) {
                return new String[0];
            }
            String base = f.getCanonicalPath();
            if (!base.endsWith(File.separator)) {
                base += File.separator;
            }
            for (int i = 0, len = list.length; i < len; i++) {
                list[i] = base + list[i];
            }
            return list;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new String[] {};
    }


    /**
     * Create a new full text index for a table and column list. Each table may
     * only have one index at any time.
     *
     * @param conn the connection
     * @param schema the schema name of the table (case sensitive)
     * @param table the table name (case sensitive)
     * @param columnList the column list (null for all columns)
     */
    public static void createIndex(Connection conn, String schema, String table, String columnList) throws SQLException {
        init(conn);
        PreparedStatement prep = conn.prepareStatement("INSERT INTO " + SCHEMA
                + ".INDEXES(SCHEMA, TABLE, COLUMNS) VALUES(?, ?, ?)");
        prep.setString(1, schema);
        prep.setString(2, table);
        prep.setString(3, columnList);
        prep.execute();
        createTrigger(conn, schema, table);
        indexExistingRows(conn, schema, table);
    }

    /**
     * Re-creates the full text index for this database. Calling this method is
     * usually not needed, as the index is kept up-to-date automatically.
     *
     * @param conn the connection
     */
    public static void reindex(Connection conn) throws SQLException {
        init(conn);
        removeAllTriggers(conn, TRIGGER_PREFIX);
        removeIndexFiles(conn);
        Statement stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("SELECT * FROM " + SCHEMA + ".INDEXES");
        while (rs.next()) {
            String schema = rs.getString("SCHEMA");
            String table = rs.getString("TABLE");
            createTrigger(conn, schema, table);
            indexExistingRows(conn, schema, table);
        }
    }

    /**
     * Drops all full text indexes from the database.
     *
     * @param conn the connection
     */
    public static void dropAll(Connection conn) throws SQLException {
        Statement stat = conn.createStatement();
        stat.execute("DROP SCHEMA IF EXISTS " + SCHEMA);
        removeAllTriggers(conn, TRIGGER_PREFIX);
        removeIndexFiles(conn);
    }

    /**
     * Searches from the full text index for this database.
     * The returned result set has the following column:
     * <ul><li>QUERY (varchar): the query to use to get the data.
     * The query does not include 'SELECT * FROM '. Example:
     * PUBLIC.TEST WHERE ID = 1
     * </li><li>SCORE (float) the relevance score as returned by Lucene.
     * </li></ul>
     *
     * @param conn the connection
     * @param text the search query
     * @param limit the maximum number of rows or 0 for no limit
     * @param offset the offset or 0 for no offset
     * @return the result set
     */
    public static ResultSet search(Connection conn, String text, int limit, int offset) throws SQLException {
        return search(conn, text, limit, offset, false);
    }

    /**
     * Searches from the full text index for this database. The result contains
     * the primary key data as an array. The returned result set has the
     * following columns:
     * <ul>
     * <li>SCHEMA (varchar): the schema name. Example: PUBLIC </li>
     * <li>TABLE (varchar): the table name. Example: TEST </li>
     * <li>COLUMNS (array of varchar): comma separated list of quoted column
     * names. The column names are quoted if necessary. Example: (ID) </li>
     * <li>KEYS (array of values): comma separated list of values. Example: (1)
     * </li><li>SCORE (float) the relevance score as returned by Lucene.
     * </li>
     * </ul>
     *
     * @param conn the connection
     * @param text the search query
     * @param limit the maximum number of rows or 0 for no limit
     * @param offset the offset or 0 for no offset
     * @return the result set
     */
    public static ResultSet searchData(Connection conn, String text, int limit, int offset) throws SQLException {
        return search(conn, text, limit, offset, true);
    }

    /**
     * Convert an exception to a fulltext exception.
     *
     * @param e the original exception
     * @return the converted SQL exception
     */
    protected static SQLException convertException(Exception e) {
        SQLException e2 = new SQLException("Error while indexing document", "FULLTEXT");
        e2.initCause(e);
        return e2;
    }

    /**
     * Create the trigger.
     *
     * @param conn the database connection
     * @param schema the schema name
     * @param table the table name
     */
    protected static void createTrigger(Connection conn, String schema, String table) throws SQLException {
        Statement stat = conn.createStatement();
        String trigger = StringUtils.quoteIdentifier(schema) + "." + StringUtils.quoteIdentifier(TRIGGER_PREFIX + table);
        stat.execute("DROP TRIGGER IF EXISTS " + trigger);
        StringBuilder buff = new StringBuilder("CREATE TRIGGER IF NOT EXISTS ");
        // the trigger is also called on rollback because transaction rollback
        // will not undo the changes in the Lucene index
        buff.append(trigger).
            append(" AFTER INSERT, UPDATE, DELETE, ROLLBACK ON ").
            append(StringUtils.quoteIdentifier(schema)).
            append('.').
            append(StringUtils.quoteIdentifier(table)).
            append(" FOR EACH ROW CALL \"").
            append(FullTextLucene2.FullTextTrigger.class.getName()).
            append('\"');
        stat.execute(buff.toString());
    }

    /**
     * Get the index writer/searcher wrapper for the given connection.
     *
     * @param conn the connection
     * @return the index access wrapper
     */
    protected static IndexAccess getIndexAccess(Connection conn) throws SQLException {
        String path = getIndexPath(conn);
        synchronized (INDEX_ACCESS) {
            IndexAccess access = INDEX_ACCESS.get(path);
            if (access == null) {
                try {
                    /*## LUCENE2 ##
                    boolean recreate = !IndexReader.indexExists(path);
                    Analyzer analyzer = new StandardAnalyzer();
                    access = new IndexAccess();
                    access.modifier = new IndexModifier(path, analyzer, recreate);
                    //*/
                    //## LUCENE3 ##
                    File f = new File(path);
                    Directory indexDir = FSDirectory.open(f);
                    boolean recreate = !IndexReader.indexExists(indexDir);
                    Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_30);
                    IndexWriter writer = new IndexWriter(indexDir, analyzer,
                            recreate, IndexWriter.MaxFieldLength.UNLIMITED);
                    //see http://wiki.apache.org/lucene-java/NearRealtimeSearch
                    IndexReader reader = writer.getReader();
                    access = new IndexAccess();
                    access.writer = writer;
                    access.reader = reader;
                    access.searcher = new IndexSearcher(reader);
                    //*/
                } catch (IOException e) {
                    throw convertException(e);
                }
                INDEX_ACCESS.put(path, access);
            }
            return access;
        }
    }

    /**
     * Get the path of the Lucene index for this database.
     *
     * @param conn the database connection
     * @return the path
     */
    protected static String getIndexPath(Connection conn) throws SQLException {
        Statement stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("CALL DATABASE_PATH()");
        rs.next();
        String path = rs.getString(1);
        if (path == null) {
            throw throwException("Fulltext search for in-memory databases is not supported.");
        }
        int index = path.lastIndexOf(':');
        // position 1 means a windows drive letter is used, ignore that
        if (index > 1) {
            path = path.substring(index + 1);
        }
        rs.close();
        return path;
    }

    /**
     * Add the existing data to the index.
     *
     * @param conn the database connection
     * @param schema the schema name
     * @param table the table name
     */
    protected static void indexExistingRows(Connection conn, String schema, String table) throws SQLException {
        FullTextLucene2.FullTextTrigger existing = new FullTextLucene2.FullTextTrigger();
        existing.init(conn, schema, null, table, false, Trigger.INSERT);
        String sql = "SELECT * FROM " + StringUtils.quoteIdentifier(schema) + "." + StringUtils.quoteIdentifier(table);
        ResultSet rs = conn.createStatement().executeQuery(sql);
        int columnCount = rs.getMetaData().getColumnCount();
        while (rs.next()) {
            Object[] row = new Object[columnCount];
            for (int i = 0; i < columnCount; i++) {
                row[i] = rs.getObject(i + 1);
            }
            //existing.fire(conn, null, row);
            existing.insert(row, false);
        }
        existing.commitIndex();
    }

    private static void removeIndexFiles(Connection conn) throws SQLException {
        String path = getIndexPath(conn);
        IndexAccess access = INDEX_ACCESS.get(path);
        if (access != null) {
            removeIndexAccess(access, path);
        }
        deleteRecursive(path);
    }

    /**
     * Close the index writer and searcher and remove them from the index access set.
     *
     * @param access the index writer/searcher wrapper
     * @param indexPath the index path
     */
    protected static void removeIndexAccess(IndexAccess access, String indexPath) throws SQLException {
        synchronized (INDEX_ACCESS) {
            try {
                INDEX_ACCESS.remove(indexPath);
                /*## LUCENE2 ##
                access.modifier.flush();
                access.modifier.close();
                //*/
                //## LUCENE3 ##
                access.searcher.close();
                access.reader.close();
                access.writer.close();
                //*/
            } catch (Exception e) {
                throw convertException(e);
            }
        }
    }

    /**
     * Do the search.
     *
     * @param conn the database connection
     * @param text the query
     * @param limit the limit
     * @param offset the offset
     * @param data whether the raw data should be returned
     * @return the result set
     */
    protected static ResultSet search(Connection conn, String text,
            int limit, int offset, boolean data) throws SQLException {
        SimpleResultSet result = createResultSet(data);
        if (conn.getMetaData().getURL().startsWith("jdbc:columnlist:")) {
            // this is just to query the result set columns
            return result;
        }
        if (text == null || text.trim().length() == 0) {
            return result;
        }
        try {
            IndexAccess access = getIndexAccess(conn);
            /*## LUCENE2 ##
            access.modifier.flush();
            String path = getIndexPath(conn);
            IndexReader reader = IndexReader.open(path);
            Analyzer analyzer = new StandardAnalyzer();
            Searcher searcher = new IndexSearcher(reader);
            QueryParser parser = new QueryParser(LUCENE_FIELD_DATA, analyzer);
            Query query = parser.parse(text);
            Hits hits = searcher.search(query);
            int max = hits.length();
            if (limit == 0) {
                limit = max;
            }
            for (int i = 0; i < limit && i + offset < max; i++) {
                Document doc = hits.doc(i + offset);
                float score = hits.score(i + offset);
            //*/
            //## LUCENE3 ##
            // take a reference as the searcher may change
            Searcher searcher = access.searcher;
            // reuse the same analyzer; it's thread-safe;
            // also allows subclasses to control the analyzer used.
            Analyzer analyzer = access.writer.getAnalyzer();
            QueryParser parser = new QueryParser(Version.LUCENE_30,
                    LUCENE_FIELD_DATA, analyzer);
            Query query = parser.parse(text);
            // Lucene 3 insists on a hard limit and will not provide
            // a total hits value. Take at least 100 which is
            // an optimal limit for Lucene as any more
            // will trigger writing results to disk.
            int maxResults = (limit == 0 ? 100 : limit) + offset;
            TopDocs docs = searcher.search(query, maxResults);
            if (limit == 0) {
                limit = docs.totalHits;
            }
            for (int i = 0, len = docs.scoreDocs.length;
                    i < limit && i + offset < docs.totalHits
                    && i + offset < len; i++) {
                ScoreDoc sd = docs.scoreDocs[i + offset];
                Document doc = searcher.doc(sd.doc);
                float score = sd.score;
                //*/
                String q = doc.get(LUCENE_FIELD_QUERY);
                if (data) {
                    int idx = q.indexOf(" WHERE ");
                    JdbcConnection c = (JdbcConnection) conn;
                    Session session = (Session) c.getSession();
                    Parser p = new Parser(session);
                    String tab = q.substring(0, idx);
                    ExpressionColumn expr = (ExpressionColumn) p.parseExpression(tab);
                    String schemaName = expr.getOriginalTableAliasName();
                    String tableName = expr.getColumnName();
                    q = q.substring(idx + " WHERE ".length());
                    Object[][] columnData = parseKey(conn, q);
                    result.addRow(
                            schemaName,
                            tableName,
                            columnData[0],
                            columnData[1],
                            score);
                } else {
                    result.addRow(q, score);
                }
            }
            /*## LUCENE2 ##
            // TODO keep it open if possible
            reader.close();
            //*/
        } catch (Exception e) {
            throw convertException(e);
        }
        return result;
    }

    /**
     * Trigger updates the index when a inserting, updating, or deleting a row.
     */
    public static class FullTextTrigger implements Trigger {

        protected String schema;
        protected String table;
        protected int[] keys;
        protected int[] indexColumns;
        protected String[] columns;
        protected int[] columnTypes;
        protected String indexPath;
        protected IndexAccess indexAccess;

        /**
         * INTERNAL
         */
        public void init(Connection conn, String schemaName, String triggerName,
                String tableName, boolean before, int type) throws SQLException {
            this.schema = schemaName;
            this.table = tableName;
            this.indexPath = getIndexPath(conn);
            this.indexAccess = getIndexAccess(conn);
            ArrayList<String> keyList = New.arrayList();
            DatabaseMetaData meta = conn.getMetaData();
            ResultSet rs = meta.getColumns(null,
                    escapeMetaDataPattern(schemaName),
                    escapeMetaDataPattern(tableName),
                    null);
            ArrayList<String> columnList = New.arrayList();
            while (rs.next()) {
                columnList.add(rs.getString("COLUMN_NAME"));
            }
            columnTypes = new int[columnList.size()];
            columns = new String[columnList.size()];
            columnList.toArray(columns);
            rs = meta.getColumns(null,
                    escapeMetaDataPattern(schemaName),
                    escapeMetaDataPattern(tableName),
                    null);
            for (int i = 0; rs.next(); i++) {
                columnTypes[i] = rs.getInt("DATA_TYPE");
            }
            if (keyList.size() == 0) {
                rs = meta.getPrimaryKeys(null,
                        escapeMetaDataPattern(schemaName),
                        tableName);
                while (rs.next()) {
                    keyList.add(rs.getString("COLUMN_NAME"));
                }
            }
            if (keyList.size() == 0) {
                throw throwException("No primary key for table " + tableName);
            }
            ArrayList<String> indexList = New.arrayList();
            PreparedStatement prep = conn.prepareStatement(
                    "SELECT COLUMNS FROM " + SCHEMA
                    + ".INDEXES WHERE SCHEMA=? AND TABLE=?");
            prep.setString(1, schemaName);
            prep.setString(2, tableName);
            rs = prep.executeQuery();
            if (rs.next()) {
                String cols = rs.getString(1);
                if (cols != null) {
                    for (String s : StringUtils.arraySplit(cols, ',', true)) {
                        indexList.add(s);
                    }
                }
            }
            if (indexList.size() == 0) {
                indexList.addAll(columnList);
            }
            keys = new int[keyList.size()];
            setColumns(keys, keyList, columnList);
            indexColumns = new int[indexList.size()];
            setColumns(indexColumns, indexList, columnList);
        }

        /**
         * INTERNAL
         */
        public void fire(Connection conn, Object[] oldRow, Object[] newRow)
                throws SQLException {
            if (oldRow != null) {
                if (newRow != null) {
                    // update
                    if (hasChanged(oldRow, newRow, indexColumns)) {
                        delete(oldRow);
                        insert(newRow, true);
                    }
                } else {
                    // delete
                    delete(oldRow);
                }
            } else if (newRow != null) {
                // insert
                insert(newRow, true);
            }
        }

        /**
         * INTERNAL
         */
        public void close() throws SQLException {
            if (indexAccess != null) {
                removeIndexAccess(indexAccess, indexPath);
                indexAccess = null;
            }
        }

        /**
         * INTERNAL
         */
        public void remove() {
            // ignore
        }
        
        public void commitIndex() throws SQLException {
            try {
                indexAccess.writer.commit();
                // recreate Searcher with the IndexWriter's reader.
                indexAccess.searcher.close();
                indexAccess.reader.close();
                IndexReader reader = indexAccess.writer.getReader();
                indexAccess.reader = reader;
                indexAccess.searcher = new IndexSearcher(reader);
            } catch (IOException e) {
                throw convertException(e);
            }
        }

        /**
         * Add a row to the index.
         *
         * @param row the row
         */
        protected void insert(Object[] row, boolean commitIndex) throws SQLException {
            /*## LUCENE2 ##
            String query = getQuery(row);
            Document doc = new Document();
            doc.add(new Field(LUCENE_FIELD_QUERY, query,
                    Field.Store.YES, Field.Index.UN_TOKENIZED));
            long time = System.currentTimeMillis();
            doc.add(new Field(LUCENE_FIELD_MODIFIED,
                    DateTools.timeToString(time, DateTools.Resolution.SECOND),
                    Field.Store.YES, Field.Index.UN_TOKENIZED));
            StatementBuilder buff = new StatementBuilder();
            for (int index : indexColumns) {
                String columnName = columns[index];
                String data = asString(row[index], columnTypes[index]);
                // column names that start with _ must be escaped to avoid conflicts
                // with internal field names (_DATA, _QUERY, _modified)
                if (columnName.startsWith(LUCENE_FIELD_COLUMN_PREFIX)) {
                    columnName = LUCENE_FIELD_COLUMN_PREFIX + columnName;
                }
                doc.add(new Field(columnName, data,
                        Field.Store.NO, Field.Index.TOKENIZED));
                buff.appendExceptFirst(" ");
                buff.append(data);
            }
            Field.Store storeText = STORE_DOCUMENT_TEXT_IN_INDEX ?
                    Field.Store.YES : Field.Store.NO;
            doc.add(new Field(LUCENE_FIELD_DATA, buff.toString(), storeText,
                    Field.Index.TOKENIZED));
            try {
                indexAccess.modifier.addDocument(doc);
            } catch (IOException e) {
                throw convertException(e);
            }
            //*/
            //## LUCENE3 ##
            String query = getQuery(row);
            Document doc = new Document();
            doc.add(new Field(LUCENE_FIELD_QUERY, query,
                    Field.Store.YES, Field.Index.NOT_ANALYZED));
            long time = System.currentTimeMillis();
            doc.add(new Field(LUCENE_FIELD_MODIFIED,
                    DateTools.timeToString(time, DateTools.Resolution.SECOND),
                    Field.Store.YES, Field.Index.NOT_ANALYZED));
            StatementBuilder buff = new StatementBuilder();
            for (int index : indexColumns) {
                String columnName = columns[index];
                String data = asString(row[index], columnTypes[index]);
                // column names that start with _
                // must be escaped to avoid conflicts
                // with internal field names (_DATA, _QUERY, _modified)
                if (columnName.startsWith(LUCENE_FIELD_COLUMN_PREFIX)) {
                    columnName = LUCENE_FIELD_COLUMN_PREFIX + columnName;
                }
                doc.add(new Field(columnName, data,
                        Field.Store.NO, Field.Index.ANALYZED));
                buff.appendExceptFirst(" ");
                buff.append(data);
            }
            Field.Store storeText = STORE_DOCUMENT_TEXT_IN_INDEX ?
                    Field.Store.YES : Field.Store.NO;
            doc.add(new Field(LUCENE_FIELD_DATA, buff.toString(), storeText,
                    Field.Index.ANALYZED));
            try {
                indexAccess.writer.addDocument(doc);
                if (commitIndex) {
                    indexAccess.writer.commit();
                    // recreate Searcher with the IndexWriter's reader.
                    indexAccess.searcher.close();
                    indexAccess.reader.close();
                    IndexReader reader = indexAccess.writer.getReader();
                    indexAccess.reader = reader;
                    indexAccess.searcher = new IndexSearcher(reader);
                }
            } catch (IOException e) {
                throw convertException(e);
            }
            //*/
        }

        /**
         * Delete a row from the index.
         *
         * @param row the row
         */
        protected void delete(Object[] row) throws SQLException {
            String query = getQuery(row);
            try {
                Term term = new Term(LUCENE_FIELD_QUERY, query);
                /*## LUCENE2 ##
                indexAccess.modifier.deleteDocuments(term);
                //*/
                //## LUCENE3 ##
                indexAccess.writer.deleteDocuments(term);
                //*/
            } catch (IOException e) {
                throw convertException(e);
            }
        }

        private String getQuery(Object[] row) throws SQLException {
            StatementBuilder buff = new StatementBuilder();
            if (schema != null) {
                buff.append(StringUtils.quoteIdentifier(schema)).append('.');
            }
            buff.append(StringUtils.quoteIdentifier(table)).append(" WHERE ");
            for (int columnIndex : keys) {
                buff.appendExceptFirst(" AND ");
                buff.append(StringUtils.quoteIdentifier(columns[columnIndex]));
                Object o = row[columnIndex];
                if (o == null) {
                    buff.append(" IS NULL");
                } else {
                    buff.append('=').append(FullText.quoteSQL(o, columnTypes[columnIndex]));
                }
            }
            return buff.toString();
        }
    }

    /**
     * A wrapper for the Lucene writer and searcher.
     */
    static class IndexAccess {

        /**
         * The index modified.
         */
        /*## LUCENE2 ##
        IndexModifier modifier;
        //*/

        /**
         * The index writer.
         */
        //## LUCENE3 ##
        IndexWriter writer;
        //*/

        /**
         * The index reader.
         */
        //## LUCENE3 ##
        IndexReader reader;
        //*/

        /**
         * The index searcher.
         */
        //## LUCENE3 ##
        Searcher searcher;
        //*/
    }

}
